The set of viable design elements available for animals to use in building skeletons has been fully exploited. Analysis animal relation the multivariate, theoretical "Skeleton Space" shown that a large proportion these options are used each phylum. Here, we show structural deployed Burgess Shale (Middle Cambrian) incorporate 146 182 character pairs defined this morphospace. Within 15 million years appearance crown groups phyla with substantial hard parts, at least 80 percent skeletal...

The structures of animal skeletons converge repeatedly on a limited number architectural designs that can be constructed by growing organisms and are functionally viable, although often not optimal. Properties materials, construction rules determine patterns development, physical constraints exerted the requirements function suggest organic structure must necessarily approach these recurrent elements design. A set potential for is derived in terms geometric properties materials. Skeletons...

Growth processes and patterns set functional limits on the adaptive range of organisms that have evolved a particular “Bauplan.” The design elastic ligament has played large part in determining scope evolutionary radiation Arcoida. Tensional lamellar compressional fibrous materials this ligament, which appear to be similar their properties those other bivalves, are not segregated positions where they could best perform different mechanical functions. growth unspecialized exhibits strong...

Arcoid bivalves occupy an intermediate position, in terms both of morphology and adaptive range between the Pterioida Veneroida. The limits arcoid adaptations are related to growth patterns their shells. Both hinge ligament grow by serial repetition simple structures, contrast with development more specialized, complex structures other groups. These place significant mechanical constraints on possible shell forms. Most arcoids live moderately unstable environments, where they liable be...

Abstract Exceptionally well‐preserved impressions of two bundles bristles protrude from the apertures small, spiral shells Pelagiella exigua , recovered Kinzers Formation (Cambrian, Stage 4, ‘ Olenellus Zone’, c . 512 Ma) Pennsylvania. These are inferred to represent clusters chitinous chaetae, comparable those borne by annelid parapodia and some larval brachiopods. They provide an affirmative test in early metazoan fossil record inference, phylogenetic analyses living taxa, that chaetae a...

SYNOPSIS. Bivalved, exoskeletal shells have evolved independently in brachiopods, several groups of molluscs, ostracodes, conchostracans, phyllocarids, and the Paleozoic rugose coral Calceola. Composed a variety usually composite organic mineral materials, they may be rigid or somewhat flexible. Shell growth can occur only by accretion at margins over inner surfaces valves. Isometric produces logarithmic spiral cones, paradigms from which real depart slightly very far, allometric response to...

The evolution, of the arcoid bivalves is a consequence interaction three distinct, complementary groups factors which determine organic form. Arcoid diversity has resulted from opportunistic realization possible forms, within range set by limitations ancestral morphology, characteristic growth patterns, and requirements survival in available environments. Historical, phylogenetic constraints include evolutionary heritage common to all bivalves, filibranch gill, shell microstructure suited...

Abstract The dorsal ligaments of arcoid bivalves typically consist oblique, lamellar and fibrous sheets, alternating along the hinge so that their attachments from characteristic chevron patterns. New elements are added at or near middle pattern, as ligament grows ventrally gets longer. Most Palaeozoic arcoids exhibit this growth which still predominates among living descendants. Early in Cretaceous, a novel pattern emerged, with vertical strips embedded grooves sheet is attached to each...

Seilacher, A. & Thomas, R.D.K. 2011: Self-organization and emergent individuality of favositid corals adapted to live on soft substrates. Lethaia, Vol. 45, pp. 2–13. Secondary soft-bottom dwellers share the problem that their ancestors, attached hard substrates, had lost mobility. On only a limited number alternative tricks are available maintain sessile organisms in life position or right them following disturbance. Consequently, convergent adaptations have emerged unrelated members this...

Previous testing has indicated that holographic radar can image surficial and shallowly-buried dinosaur tracks if the track surface presents a dielectric contrast. This paper reports on blind scanning of stratigraphic surfaces just above known, exposed trackways. Testing at Valley Quarries Fairfield operation near Gettysburg, PA yielded mixed results could not be ground-truthed. Additional was conducted famous rock Dinosaur State Park in Rocky Hill, CT, where large Eubrontes Grallator are...

Two apparently contradictory models have been proposed, relating the disposition of microstructural fabrics bivalve shell to stresses they experience. These are here shown apply function in different circumstances. In its day-to-day operation, acts as a pair beams, loaded under opposing exerted by adductor muscles and ligament. The resulting strain is built into new layers added growing interior surface (Wainwright 1969). distribution induced attempts crush shell, or violent adduction...

Modern bivalves display a latitudinal life history gradient (LLHG): tropical tend to grow fast and die young, whereas mid- high-latitude typically more slowly may live much longer. Environmental factors such as temperature seasonal food availability, both of which affect metabolic rates, are thought be partially responsible for this pattern. Given that influences histories, we predict the expression individual gradients should vary over time with changes in global climate. Here, use internal...

The origin and diversification of terrestrial communities has long been associated with the Devonian. earliest known substantial assemblage land plants animals preserved in or close to their original habitats is still that Rhynie Chert peat bog, from Scotland, which Siegenian age.